1. Field of the Invention
The present invention relates to an antibody-binding polypeptide, an antibody-binding fusion polypeptide, and an adsorption material.
2. Description of the Related Art
In recent years, the development of antibody drugs is booming. This is because antibody drugs making use of human immune function can be expected to have a high efficacy and also exhibit relatively low side effects, whereby such antibody drugs are believed to be as the center of medical treatment in the future. The technology essential to the development and practical applications of antibody drugs is a continuous, large-scale, and high-speed purification technique of antibodies. The currently most commonly used method for the purification of antibodies is affinity chromatography using protein A.
Protein A is a membrane protein present in the cell wall of Staphylococcus aureus and is known to have a strong binding ability to the constant region (Fc region, Fc=Fragment, crystallizable) of an antibody molecule. Since common structures are conserved in the constant region across classes and subclasses of various antibody molecules, affinity chromatography using protein A as an antibody-binding ligand can be used for the purification of various kinds of antibody molecules against which antigens are different.
However, since protein A is produced using a genetic engineering method, there is a problem that production processes are complicated, consequently resulting in high production costs. Further, protein A could not be used with several times of repeated washing, due to having insufficient alkali resistance and temporal stability, and a short lifetime resulting from severe degradation caused by alkali washing of a column. For these reasons, costs of antibody purification were likely to be high.
To cope with such problems, for example, Li, R., Dowd, V., Steward, D. J., Burton, S. J., and Lowe, C. R., 1998, Nature Biotechnology, Vol. 16, pp. 190 to 195 discloses a low molecular weight compound ApA (acronym standing for “Artificial protein A”) that can be prepared according to the following reaction scheme, from a dipeptide consisting of phenylalanine 132 and tyrosine 133 of protein A as a mimetic ligand for protein A.
